Optical-chemical sensors based on plasmonic phenomena modulated via micro-holes in plastic optical fibers filled by molecularly imprinted polymers

A novel optical chemical sensing approach is presented and successfully tested in this work. The device is based on modified plastic optical fibers (POFs), with molecularly imprinted polymers (MIPs) inside, coupled with a surface plasmon resonance (SPR) in POFs. The MIP is deposited in a microstructured POF platform which is used to launch the light into the SPR-POF sensor. Therefore, the SPR sensor is not directly in contact neither with the MIP layer, nor to the sample under examination and the sensor system has been made insensitive both to the MIP thickness and refractive index. The chemical sensing platform interacts with the analyte changing the effective refractive index of the POF core, and the SPR conditions at the SPR sensor. As a proof of concept, a MIP receptor specific for furfural (2-FAL) in water is used to realize the proposed sensing principle. A detection limit (LOD) of fractions of μg/l was obtained, about 2 orders of magnitude lower than that obtained with another SPR-POF sensor where the same MIP receptor was directly deposited upon the SPR-sensitive surface to detect 2-FAL in water.